x86/sgx: Log information when a node lacks an EPC section

For optimized performance, firmware typically distributes EPC sections
evenly across different NUMA nodes. However, there are scenarios where
a node may have both CPUs and memory but no EPC section configured. For
example, in an 8-socket system with a Sub-Numa-Cluster=2 setup, there
are a total of 16 nodes. Given that the maximum number of supported EPC
sections is 8, it is simply not feasible to assign one EPC section to
each node. This configuration is not incorrect - SGX will still operate
correctly; it is just not optimized from a NUMA standpoint.

For this reason, log a message when a node with both CPUs and memory
lacks an EPC section. This will provide users with a hint as to why they
might be experiencing less-than-ideal performance when running SGX
enclaves.

Suggested-by: Dave Hansen <dave.hansen@intel.com>
Signed-off-by: Aaron Lu <aaron.lu@intel.com>
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Reviewed-by: Jarkko Sakkinen <jarkko@kernel.org>
Acked-by: Kai Huang <kai.huang@intel.com>
Link: https://lore.kernel.org/all/20240905080855.1699814-3-aaron.lu%40intel.com

diff --git a/arch/x86/kernel/cpu/sgx/main.c b/arch/x86/kernel/cpu/sgx/main.c
index 6aeeb43dd3f6a8e23c29e2816051bcdea41e5561..f3f1461273ee0f9bf277a16a4a29b3c6d9ab73f6 100644 (file)
--- a/arch/x86/kernel/cpu/sgx/main.c
+++ b/arch/x86/kernel/cpu/sgx/main.c
@@ -848,6 +848,13 @@ static bool __init sgx_page_cache_init(void)
                return false;
        }
 
+       for_each_online_node(nid) {
+               if (!node_isset(nid, sgx_numa_mask) &&
+                   node_state(nid, N_MEMORY) && node_state(nid, N_CPU))
+                       pr_info("node%d has both CPUs and memory but doesn't have an EPC section\n",
+                               nid);
+       }
+
        return true;
 }